drm: rip out dev->devname

This was only ever used to pretty-print the irq driver name. And on
kms systems due to set_version bonghits we never set up the prettier
name, ever. Which make this a bit pointless.

Also, we can always dig out the driver-instance/irq relationship
through other means, so this isn't that useful. So just rip it out to
simplify the set_version/set_busid insanity a bit.

Also delete the temporary busname from drm_pci_set_busid, it's now
unused.

v2: Rebase on top of the new host1x drm_bus for tegra.

Reviewed-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_ioctl.c

@@ -72,9 +72,6 @@ static void
 drm_unset_busid(struct drm_device *dev,
 		struct drm_master *master)
 {
-	kfree(dev->devname);
-	dev->devname = NULL;
-
 	kfree(master->unique);
 	master->unique = NULL;
 	master->unique_len = 0;